In general, a canned motor pump at its rotary portion is completely immersed in a treating liquid and has not any sealing portions, so that complete non-leakage may be achieved, and thus has been recommended for use in various processing pumps. In such a type of canned motor pumps, all radial and thrust loads of the rotary portions during operation may be received by the slide bearing supporting a rotary shaft of the rotary portions. Since the bearing is immersed in the treating liquid as mentioned above, a special monitoring apparatus should be provided for monitoring abrasion of the bearing.
In the following, such a monitoring apparatus will be described briefly. The monitoring apparatus may generally be mechanical or electrical, but a mechanical embodiment of the apparatus will be described with reference to FIG. 18. The monitoring apparatus has a slide bearing 10 for supporting a canned motor shaft 12 provided at its end with an end nut 14, within a hollow portion 16 of which is arranged a sensing portion 20 of a detector 18. The sensing portion 20 is sealed under pressure therein. In such construction, radial abrasion of the bearing 10 generates an eccentric movement of the shaft 12, whereas thrust abrasion of the bearing 10 displaces the shaft 12 axially, resulting in contact (and hence breakage) of the sensing portion 20 with an inner wall or end face of the hollow portion 16. Thus, fluctuations of an inner pressure of the sensing portion 20 are sensed for detecting the limiting abrasion in the radial and thrust direction of the bearing 10. In the apparatus of an electrical construction not specifically shown, on the other hand, a plurality of coils for detecting a magnetic flux are connected in series and placed within a stator, for example. In such a construction, abrasion of the bearing causes the shaft and a rotor to rotate eccentrically, thereby to increase an electromotive force in the detecting coil for detecting the abrasion degree of the bearing.
These conventional monitoring apparatus of the bearing as described above have, however, several disadvantages and problems. Firstly, the mechanical construction may detect both the radial and thrust abrasion relating to the limiting abrasion, but not an abrasion degree leading to the limiting abrasion or a residual life. The electrical construction, on the other hand, may detect the abrasion degree of the bearing only in the radial direction, but not the thrust direction.
Further, in such type of the monitoring apparatus of the bearing, it is desirable to detect both the rotating and thrust direction of the bearing. Such detection cannot be achieved by the conventional apparatus as described above.
An object of the invention, therefore, is to provide a monitoring apparatus of a bearing which may detect not only the radial and thrust abrasion degree of the bearing but also the rotating and thrust direction of the shaft.